Office ofthe Vice President for Research

October 2011

What happened?

Graduate students were performing a procedure they had used successfully in the past.
The procedure used four materials: nitric acid, hydrofluoric acid, hydrochloric acid
and peroxide, and hydrofluoric acid with ethanol. At the end of the procedure, they
disposed of each material in a separate waste bottle in a cabinet beneath the hood.

Several hours after the procedure ended, after the students had left the lab, a waste
bottle exploded. The blast blew open the doors to the cabinet and propelled 0.5 inch
glass shards about 35 feet over the length and breadth of the lab. No one was in the
lab, and there were no injuries. The Lubbock Fire Department (LFD) and HAZMAT team
responded and cleaned up the laboratory.

Area where incident occurred before LFD HAZMAT team cleanup.

One of two 500 ml bottles of nitric acid that were broken.

Two 500 ml bottles of hydrofluoric acid that were punctured.

Red dots on floor indicate glass shards at the end of the lab farthest from explosion
in the hood.

What was the cause?

The explosion was likely caused by a reaction between nitric acid and ethanol, created
when nitric acid waste was mixed with the hydrofluoric acid + ethanol waste. These
wastes were mixed in a glass bottle, the expected oxidative reaction occurred, pressure
built up, and the bottle exploded. This is the reaction expected when nitric acid is combined with organics – no surprises at all.

Why did the wastes get mixed together? Likely reasons:

The waste bottle was not externally polymer coated (which could have minimized glass
fragmentation in the event the bottles were over-pressured or dropped).

The waste bottle label was not color-coded to indicate the type of waste present in
each container.

The waste bottle did not have a venting cap that could have mitigated over-pressurization.

The top of the lab waste storage bottle was very tightly capped, which could have
result in over-pressurization and catastrophic failure of the bottle.

The experimenters may have not understood the printed text on the laboratory waste
bottle. S/he may not have understood chemical names printed in English.

What corrective actions were taken?

EH&S closed the laboratory, reviewed chemical storage and waste handling procedures
with the students and PIs, and retrained laboratory personnel in appropriate handling,
storage, and waste procedures for nitric acid.

Extensive guidance about waste handling was provided to the TTU community via e-mails
and a website story about hazardous waste procedures: